self.transitionAnimator = [[ARTransitionAnimator alloc] init];
 self.transitionAnimator.transitionDuration = 0.6;
 self.transitionAnimator.transitionStyle = ARTransitionStyleMaterial|ARTransitionStyleLeftToRight;

 FirstViewController *viewController = [[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
 self.navigationController.delegate = self.transitionAnimator; // set delegate
 [self.navigationController pushViewController:viewController animated:YES];